This is a harmonica with octave tuning (the upper row of 20 holes is tuned one octave below the lower row of 20). When the 2 rows are played at the same time this creates an effect of 2 harmonicas simultaneously playing the same melody. This enables a single player to achieve a stronger, full-bodied sound not possible while playing a standard diatonic.Echo harmonicas offer comfortable curved mouthpieces with traditional wood combs. The chrome-plated covers have turned-in ends for extra style and sound. Key of C.